how can I access. my iCloud mail

What do you mean by access your iCloud mail? Did you forget your iCloud email address? Do you want to set up the email address in the Mail app? More information would help.

If you forgot the address, see if you can recover the ID/password. Use every email address you can think of.

Apple ID - How to find your Apple    An iCloud e-mail address is an Apple ID.

Apple ID - Find             

If you want to set up the email account in the Mail app.

Mail – Setup on a device